Rotor disk for an exhaust turbocharger, exhaust turbocharger and method for balancing a rotor assembly for an exhaust turbocharger

ABSTRACT

A rotor disk for an exhaust turbocharger is mounted in a housing of the exhaust turbocharger so as to be able to rotate about an axis of rotation. The rotor disk has a disk hub including a disk back and a disk front facing away from the disk back. A plurality of rotor disk blades are formed on the disk hub in a manner extending between the disk back and the disk front. A balancing mark is arranged in a blade channel formed between a first blade of the plurality of rotor disk blades and a second blade, arranged adjacent to the first blade, of the plurality of rotor disk blades. The balancing mark is triangle-like. The disclosure also relates to an exhaust turbocharger comprising such a rotor disk and to a method for balancing a rotor assembly for such an exhaust turbocharger.

TECHNICAL FIELD

The invention relates to a rotor disk for an exhaust turbocharger, an exhaust turbocharger and to a method for balancing a rotor assembly for an exhaust turbocharger.

BACKGROUND

Laid-open document DE 10 2010 048 099 A1 discloses a rotor assembly comprising a rotor disk of an exhaust turbocharger. The rotor disk has rotor disk blades which are arranged on a disk hub, comprising a disk back and a disk front facing away from the disk back. An arcuate balancing mark is introduced into the rotor disk on the disk back.

A rotor assembly which has a pear segment-shaped balancing mark can be found in laid-open document DE 10 2015 219 374 A1. This pear segment-shaped balancing mark thus has a basic body which has a head which is formed substantially smaller in comparison with the basic body. It is problematic that the basic body is arranged facing towards a disk centre, whereas the head is positioned facing towards a disk outer edge. This means that, by reason of a blade channel which tapers in the direction of the disk centre and has a balancing mark formed in this manner, a delimitation is provided in terms of material removal for eliminating the imbalance.

It is likewise known to introduce balancing marks into the hub between the disk back and the disk front. In a blade channel formed between two rotor disk blades, the balancing mark is arranged in the channel base thereof. However, in certain circumstances an insufficient amount of removable mass may be available in this region because preferably the balancing mark is placed in the region of a largest disk diameter of the rotor disk, in which typically a minimum wall thickness is present. In the worst case scenario, this then results in an increased reject rate.

In the case of balancing marks which are produced by milling, high material stresses occur in the base of the balancing mark, i.e. in the region of the smallest thickness of the rotor disk. This means that, in order to reduce or eliminate the imbalance, a sufficient amount of material is removed over the thickness of the rotor disk by material removal.

SUMMARY

The object of the present invention is to provide an improved rotor disk for an exhaust turbocharger, such an exhaust turbocharger and a method for balancing a rotor assembly of such an exhaust turbocharger, thus facilitating improved balancing.

This object is achieved by a rotor disk for an exhaust turbocharger as disclosed in this paper, by an exhaust turbocharger as disclosed in this paper and by a method for balancing a rotor assembly for an exhaust turbocharger as disclosed in this paper.

The first aspect of the disclosure relates to a rotor disk for an exhaust turbocharger which is mounted in a housing of the exhaust turbocharger so as to be able to rotate about an axis of rotation. The rotor disk has a disk hub comprising a disk back and a disk front facing away from the disk back. Formed in a manner extending between the disk hub and the disk back is a plurality of rotor disk blades, wherein a balancing mark is arranged in a blade channel formed between a first blade of the plurality of rotor disk blades and a second blade, arranged adjacent to the first blade, of the plurality of rotor disk blades. The balancing mark is triangle-like, preferably triangular.

The advantage is an enlargement of the balancing mark without compromising a minimum thickness of the rotor disk because material is removed in three dimensions in order to produce the balancing mark. In other words, this means that material is removed in the direction of a longitudinal axis of the rotor disk, therefore into the depth of the rotor disk or into the thickness of the rotor disk, in the circumferential direction and in the radial direction of the rotor disk. Since material is removed in the three directions mentioned, substantially more material can be removed without compromising the strength of the rotor disk in operation, in comparison with the balancing marks of the prior art. This means that a reject rate of the produced rotor disks can be substantially reduced.

A stress maximum of the milling is at the edge of the milling, i.e. in other words in a region with a greater material thickness of the rotor disk than is provided e.g. in a centre of the balancing mark, as is present e.g. in the case of point-shaped balancing marks.

By reason of this design of the balancing mark, a rotor assembly, to which the rotor disk is allocated and which comprises a shaft, to which the rotor disk is to be connected or is connected for conjoint rotation therewith, can be balanced in a particularly effective manner such that the rotor assembly can perform a particularly effective and at least almost imbalance-free rotational movement during the operation of the exhaust turbocharger.

In one embodiment, a limb of the balancing mark is arranged extending in the circumferential direction. The advantage resides in an optimised use of a channel base of the blade channel which is configured so as to taper starting from the disk outer edge of the rotor disk in the direction of a disk centre of the rotor disk and is configured so as to be approximately triangle-like. Therefore, the two further limbs of the triangle-like balancing mark, when adapted to the existing channel base, can be arranged extending in the direction of the disk centre in order to achieve the required removal of material.

Since typically stress close to the rotor disk blade is low, it is advantageous to form the balancing mark close to the rotor disk blade.

In a further embodiment, a mark base of the balancing mark is smaller than a free surface of the balancing mark. In other words, this means that the limbs of the balancing mark are formed so as to taper in the direction of the disk back. The advantage can be seen in a reduction in notch stress because a rounded transition, at least one without sharp edges, can be formed between the mark base and the limbs.

In particular, the balancing mark is advantageously suitable for a compressor wheel which, comparison with a turbine wheel, has a lower wall thickness between the disk back and the disk front in particular on a disk outer edge. The reduction in the wall thickness serves not only to reduce a mass moment of inertia of the rotor disk but also to reduce material, whereby material costs of the rotor disk are likewise reduced and therefore the compressor wheel can be produced in a cost-effective manner. Since the balancing mark is triangle-like, the periphery of the balancing mark, where the balancing mark extends to a low depth, can be adapted such that sufficient removal of material can be achieved in order to produce an imbalance-free rotor disk.

The second aspect of the disclosure relates to an exhaust turbocharger, in particular for an internal combustion engine, comprising a rotor assembly which is rotatably mounted in a housing and comprises a shaft and at least one rotor disk which is connected to the shaft for conjoint rotation therewith. Advantageous embodiments of the first aspect of the disclosure are to be considered to be advantageous embodiments of the second aspect of the disclosure and vice versa.

The rotor assembly of the exhaust turbocharger has a particularly calm rotational movement as a result of the advantageous balancing of the rotor disk and in particular of the rotor assembly, which is conducive to an efficient operation of the exhaust turbocharger and to a long service life thereof.

The third aspect of the disclosure relates to a method for balancing a rotor assembly, which is to be mounted rotatably in a housing of an exhaust turbocharger, in particular a rotor disk of a rotor assembly which has a plurality of rotor disk blades on a disk hub of the rotor disk. Formed between at least one first blade of the plurality of rotor disk blades and a second blade, adjacent to the first blade, of the plurality of rotor disk blades is a blade channel comprising a channel base in which a balancing mark is formed. Provision is made that the balancing mark is produced using high speed balancing.

One advantage can be seen in the fact that with the aid of the high speed balancing method it is possible to balance the rotor assembly completely, not just the individual rotor disks independently of one another, in one procedure, whereby a substantial time reduction is achieved during balancing of the rotor assembly. Furthermore, a residual imbalance of the turbine wheel can be corrected e.g. when adding the balancing mark to the compressor wheel. Imbalances occurring by reason of elastic effects can likewise be corrected.

The balancing mark is produced in a cost-effective manner by a material-removal method, in other words by means of material removal, wherein preferably a milling method is used. In an advantageous manner, a ball head-shaped tool is used so that in the region of converging edges and/or surfaces, connecting elements and/or transitions can be rounded. The advantage can be seen in a substantial reduction in notch stresses which occur in the region of sharp, i.e. non-rounded, connecting elements and/or transitions, as are formed e.g. during use of a cylinder head milling tool, and can result in the failure of the rotor disk or the rotor assembly.

Further advantages, features and details will be apparent from the following description of preferred exemplified embodiments and with reference to the drawing. The features and combinations of features mentioned earlier in the description and the features and combinations of features mentioned hereinunder in the description of the figures and/or illustrated in the figures alone can be employed not only in the combination stated in each case but also in other combinations or on their own without departing from the scope of the invention. Like or functionally identical elements are allocated identical reference signs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a detail of a rotor disk according to the prior art.

FIG. 2 shows a perspective view of a detail of a further rotor disk according to the prior art.

FIG. 3 shows a perspective view of a detail of a rotor disk in a first exemplified embodiment.

FIG. 4 shows a perspective view of a detail of a rotor disk in a second exemplified embodiment.

FIG. 5 shows a perspective view of a detail of a rotor disk in a third exemplified embodiment.

FIG. 6 shows a perspective view of a detail of a rotor disk in a fourth exemplified embodiment.

DETAILED DESCRIPTION

A rotor disk 1 of a rotor assembly 2 for an exhaust turbocharger 3 according to the prior art is formed as shown in FIG. 1. The rotor disk 1 is designed in the form of a compressor wheel. The rotor assembly 2 comprises the compressor wheel 1 and a turbine wheel, not illustrated in greater detail, which is connected via a shaft, not illustrated in greater detail, to the compressor wheel 1 for conjoint rotation therewith.

The rotor assembly 2 is mounted in a bearing portion, not illustrated in greater detail, of the exhaust turbocharger 3 so as to be able to rotate about an axis of rotation, not illustrated in greater detail, of the rotor assembly 2. The turbine wheel is accommodated in a rotatable manner in an exhaust gas conducting section, not illustrated in greater detail, of the exhaust turbocharger 3, said exhaust gas conducting section being capable of having a flow pass therethrough. Exhaust gas from an internal combustion engine, which is not illustrated in greater detail and is connected to the exhaust turbocharger 3 so as to be capable of having a flow pass therethrough, is supplied via an inlet channel, not illustrated in greater detail, of the exhaust gas conducting section, to the turbine wheel, causing said turbine wheel to rotate.

By means of the rotationally-fixed connection, established with the aid of the shaft, to the compressor wheel 1, the compressor wheel 1 which is rotatably accommodated in an air conducting section, not illustrated in greater detail, is likewise caused to perform a rotational movement, wherein it takes in air and compresses it. The compressed air is supplied to the internal combustion engine via an outlet channel, not illustrated in greater detail, of the air conducting section.

The compressor wheel 1 comprises a plurality of rotor disk blades 4, by means of which it takes in air, which blades are arranged on a disk hub 5 of the compressor wheel 1. The disk hub 5 has a disk back 6 and a disk front, not illustrated in greater detail and facing away from the disk back 6, of the disk hub 5. The plurality of rotor disk blades 4 are arranged on the disk hub 5 in a manner extending from the disk front to the disk back 6. Formed between in each case two blades of the plurality of rotor disk blades 4, a first blade 7 and a second blade 8, is a blade channel 9 comprising a channel base 10, along which the air flows. The rotor disk 1 can be rotated about an axis of rotation not illustrated in greater detail.

In order to produce a particularly calm rotational movement of the rotor assembly 2, a balancing mark 11 is formed on the channel base 10 of the compressor wheel 1. The balancing mark 11 of the rotor disk according to the prior art, as illustrated in FIG. 1, is point-shaped.

FIG. 2 illustrates a further rotor disk according to the prior art. The formed balancing mark 11 is elongate and slightly curved.

A balancing mark 11 as illustrated according to a first exemplified embodiment in FIG. 3 is triangle-like. The balancing mark 11 has a first limb 12, a second limb 13 and a third limb 14 which are connected to one another with the aid of connecting elements 15. The connecting elements 15 are curved, whereas the limbs 12, 13, 14 are substantially linear relative to the connecting elements 15.

The triangle-like balancing mark 11 is triangle-like predominantly in relation to its periphery. However, it could likewise be triangle-like in relation to its depth extension T. Or it could likewise be triangle-like, i.e. tetrahedron-like in all three dimensions. They can also be equilateral, scalene or isosceles triangles.

In order to produce the balancing mark 11 using so-called high-speed balancing, on the one hand the material-removing tool can be moved or on the other hand the rotor disk 1 or the rotor assembly 2 itself can be moved. A linear balancing mark 11 can be produced preferably by a moved tool, whereas the balancing mark 11 in accordance with the disclosure can be produced preferably with a moved rotor disk 1 or moved rotor assembly 2 and moved tool.

In the so-called high speed balancing machine, the rotor assembly is installed in the bearing housing and is clamped in the high speed balancing machine, thus allowing access for material removal at the disk hub 5 in the axial direction. If other machines are used, radial-axial machining can be effected at specific angles. This provides access to regions of the disk hub 5 which are located radially further inwards in the direction of the disk back 6 where the stresses are not so high. In this case, e.g. more material could also be removed.

In order to effect sufficient removal of a rotor disk mass which reduces, in particular eliminates, the imbalance, the depth extension T of the balancing mark 11 can likewise be increased. In comparison with the typical balancing marks, a sufficient amount of material can be removed in order to eliminate the imbalance because material is removed in three dimensions by reason of the triangle-like balancing mark 11.

The first limb 12 which can also be considered to be a base side of the balancing mark 11 is arranged extending in the circumferential extension direction U. Therefore, a tip 16 of the balancing mark 11 is positioned facing away from a disk outer edge 17 and facing towards a disk centre of the rotor disk. Therefore, the balancing mark 11 is arranged adapted virtually to an elongation of the channel base 10 which is formed so as to taper starting from the disk outer edge 17 in the direction of the disk centre.

The first limb 12 of the balancing mark 11 illustrated in FIG. 3 in a first embodiment is slightly curved, whereby the balancing mark 11 can adapt to a curvature of the disk outer edge 17. However, the curvature of the first limb 12 is substantially shallower than the curvature of the connecting elements 15. Likewise, the two other limbs 13, 14 could have a slight curvature which, however, is substantially reduced in comparison with the curvature of the connecting elements 15.

FIG. 4 illustrates the balancing mark 11 in accordance with the disclosure in a second exemplified embodiment. In comparison with the balancing mark 11 of the first exemplified embodiment, the limbs 12, 13, 14 are linear, wherein an extension is increased in the circumferential direction U of the balancing mark 11 of the second exemplified embodiment.

The curvatures of the connecting elements 15 are provided in order to reduce a notch stress between the converging limbs 12, 13, 14.

A further reduction in the notch stress is achieved by virtue of the fact that a transition 19 formed between the limbs 12, 13, 14 and a mark base 18 of the balancing mark 11 is rounded. In other words, this means that the mark base 18 is smaller than a free surface 20 of the balancing mark 11, as is evident in particular from the balancing mark 11 according to a third exemplified embodiment as illustrated in FIG. 5. The free surface 20 of the balancing mark 11 corresponds to the surface in the plane of the channel base 10, said surface extending between the limbs 12, 13, 14.

In order to produce the balancing mark 11, basically any material-removing method can be used, in other words any material removal process. In particular, grinding is feasible if the rotor disk 1 is designed in the form of a turbine wheel. Likewise, the material removal could also be achieved with the aid of a laser method. The balancing mark 11 could also be produced on an outer edge of the rotor disk 1 with the aid of a cutting method. The advantage of milling can be seen in terms of a possible surface treatment and a cost advantage over other methods because milling is cost-effective and flexible to use.

The rotor disk 1 illustrated in particular in FIG. 6 and being in the form of a compressor wheel has the balancing mark 11 which has been produced with a ball head milling tool In other words, this means that the balancing mark 11 has been formed by a milling method, in particular with a ball head-like tool. As a result, the rounded connecting elements 15 and the rounded transition 19 can be produced in a simple manner without a further machining step during the formation of the balancing mark 11 by means of material removal. 

1.-8. (canceled)
 9. A rotor disk for an exhaust turbocharger, wherein the rotor disk (1) is mounted in a housing of the exhaust turbocharger (3) so as to be able to rotate about an axis of rotation, and wherein the rotor disk (1) has a disk hub (5) comprising a disk back (6) and a disk front facing away from the disk back (6), and wherein a plurality of rotor disk blades (4) are formed on the disk hub (5) in a manner extending between the disk back (6) and the disk front, and wherein a balancing mark (11) is arranged in a blade channel (9) formed between a first blade (7) of the plurality of rotor disk blades (4) and a second blade (8), arranged adjacent to the first blade (7), of the plurality of rotor disk blades (4), and wherein the balancing mark (11) is triangle-like, and wherein a limb (12) of the balancing mark (11) is arranged extending in a circumferential direction.
 10. The rotor disk as claimed in claim 9, wherein a mark base (18) of the balancing mark (11) is smaller than a free surface (20) of the balancing mark (11).
 11. The rotor disk as claimed in claim 9, wherein the rotor disk (1) is a compressor wheel.
 12. An exhaust turbocharger comprising a rotor assembly (2) which is rotatably mounted in a housing of the exhaust turbocharger (3) and comprises a shaft and at least one rotor disk (1) as claimed in claim 9 which is connected to the shaft for conjoint rotation therewith.
 13. A method for balancing a rotor assembly (2) which is mounted rotatably in a housing of an exhaust turbocharger (3), wherein the rotor assembly (2) comprises a rotor disk (1) as in claim 9 and wherein the balancing mark (11) is produced using high speed balancing.
 14. The method as claimed in claim 13, wherein the balancing mark (11) is produced by material removal.
 15. The method as claimed in claim 13, wherein the balancing mark (11) is formed using a milling method.
 16. The method as claimed in claim 13, wherein the balancing mark (11) is formed using a milling method with a ball head-like tool. 